Isobutylene is one of the important chemical raw materials that are converted into ethyl tert-butyl ether (ETBE), paraxylene, methyl methacrylate (MMA), and the like. Among these, for example, MMA is a substance with significantly high utility value as a raw material for polymethyl methacrylate that is useful as a transparent resin. There is a method of synthesizing this MMA by using isobutylene as a starting material, as one of methods for producing the MMA.
Isobutylene as a raw material for MMA is obtained by extracting isobutylene as tert-butanol from the spent BB, which is a residue obtained by the fractional distillation of butadiene from the C4 fraction obtained by naphtha cracking, by a hydration reaction using an acid catalyst and dehydrating the extracted isobutylene. In addition, there is also a method in which methyl tert-butyl ether is once synthesized from isobutylene in the spent BB and methanol and is then decomposed. Such a conventional method for producing isobutylene uses petroleum as a raw material. Thus, the development of a novel method for producing isobutylene which does not depend on petroleum is desired in the recent situation that the depletion of petroleum is concerned.
Further, carbon dioxide generated at the time of burning petroleum is considered as a cause of global warming. In this regard, a biorefinery technology has attracted the worldwide attention as an energy and chemical producing technology from biomass of a renewable resource. The biorefinery is to produce a synthesis gas, saccharides such as glucose, and aromatic compounds such as lignin by the gasification, saccharification, and extraction of various kinds of biomass and to produce energy and chemicals by converting them in various ways. Examples of the product which is produced by the biorefinery include ethanol, butanol, and diesel oil as energy. In chemicals, it is possible to produce a significantly great number of chemicals by the derivation from key compounds (platform compounds) such as saccharide-derived succinic acid, 3-hydroxypropionic acid, and aspartic acid proposed by the US Department of Energy.
Meanwhile, it is known that isobutanol can also be produced by fermenting glucose, and isobutanol is mentioned as one of the biomass-derived raw materials. For example, it is described in Patent Literature 1, Patent Literature 2, Patent Literature 3, Patent Literature 4, Patent Literature 5, and Non-Patent Literature 1 that isobutanol can be produced by dehydrating isobutanol.